Free Wire Fill calculator with clear step-by-step results.
Fill is total cable cross-sectional area over conduit internal area. The limit exists so cables can be drawn in without stripping insulation and so heat can dissipate, and the bend count matters independently - most codes cap a run at 360 degrees of bend between draw points, which is four right angles.
Fill percentage
Fill % = cables x pi x (cable OD / 2)^2 / (pi x (conduit ID / 2)^2) x 100
Maximum cables
Max = floor(conduit area x target fill / cable area)
Conduit fill, bend radius, draw-point spacing and conductor derating are governed by electrical codes that differ by jurisdiction. Installations must be designed and inspected by a licensed electrician.
It is the code allowance for three or more conductors and balances pulling tension against thermal dissipation. One conductor is allowed 53% and two only 31%.
Yes, separately. More conductors bundled together means mutual heating, which triggers ampacity derating on top of the geometric fill limit.